The present observation that all specimens contain immunocytochemical staining of lymphocytic cells for S100A4 is consistent with previous reports that S100A4 is found in human cells cultured from the immune system, the promyelocytic leukaemia cell line, HL-60 (Takenaga et al, 1994), the acute lymphoblastic leukaemia cell line, MOLT-4, and human peripheral lymphocytes treated with interleukin 2 (Tulchinsky et al, 1995), as well as in lymphocytes associated with human breast cancer (Nikitenko et al, 2000; Rudland et al, 2000). The gene discussed is S100A4; the disease is acute promyelocytic leukemia.